Sustainable fertilization through co-application of biochar and chemical fertilizers improves yield, quality of Andrographis paniculata and soil health

Cultivation of medicinal plants by maintaining sustainable environment with low chemical inputs is attempted through a pot culture experiment by integrating the biochar prepared from lemongrass (Cymbopogon fiexuosus) distillation waste and chemical fertilizers (CF) in different ratios. The objective was to find out the influence on yield, physiology and quality of Andrographis paniculata (kalmegh) herb and on soil chemical/biological properties. All the growth parameters and yield were significantly influenced by the integrated biochar and CF application. Biochar application, remarkably improved the soil carbon content, cation exchange capacity and nutrients accessibility. However, significantly higher fresh herbage yield (140.8 g plant(-1)) was recorded in the treatment receiving biochar (5 t ha(-1)) combined with recommended dose of CF (60:20:40 NPK kg ha(-1)). The same treatment resulted in higher soil microbial biomass C, fluorescein diacetate hydrolytic, dehydrogenase and alkaline phosphatase activity. Total phenol/flavonoid contents and antioxidant (DPPH and ARTS) activities, were higher in sole biochar treated plant and increased further in combination with CF. Sole application of biochar or CF did not have any significant influence on leaf andrographolide content, however their combination increased the content but the effects were not significant on stem andrographolide. The reduction in stomatal conductance and higher water use efficiency after biochar application indicates it's potential to mitigate water deficit stress. Results indicate that use of only biochar was not enough to improve the plant growth and soil health. Therefore, to achieve environmentally safe and quality herb production, it is recommended to use combination of biochar and CF which not only improve crop yield and quality but also improves the soil quality.